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<Paper uid="C88-2125">
  <Title>IMPL~\[CI(TNESS~ A~:; A G(.lt~)I\[NG PRINC~itLE iN tV~AC~/li~NE TRANSLATION</Title>
  <Section position="4" start_page="599" end_page="600" type="evalu">
    <SectionTitle>
4. Implicitness
</SectionTitle>
    <Paragraph position="0"> Since there are no cross-linguistically valid semantic relations, and since case frames arc therefore language-specific, the transfer step actually lacks a language-independent intermediate stage. This means that, where semantic relations are concerned, there is no tree pivot. There are only source structures and target structures with a transfer step somewhere between them. Given the notorious difficulties of defining deep cases,  the question arises whether it is really necessary for machine translation to make semantic relations explicit. As they are language-specific anyway, it is much easier to perform transfer at another level, which is language-specific as well, but about which there is much more certainty: syntax. If transfer is carded out at the syntactic level, semantic deep cases can remain implicit.</Paragraph>
    <Paragraph position="1"> Before describing this in somewhat more detail, a few words about the semantic elements. If there are no language-independent semantic relations, looking for language-independent semantic elements does not seem worthwhile either. Yet, the above discussion of the function of an intermediate representation entails another unexpected implication: Since an intermediate representation is the only link between source and target languages, it must be as expressive as any of them. If high-quality machine translation is the goal, this condition is inevitable, since the intermediate representation has to render and to convey the full and unsimplified content of the text, to make further translation possible. It must be feasible to translate into such an intermediate representation from all other languages. Interestingly enough, this translatability criterion is the property by which human language is distinguished from artificial symbol systems by one of the classics of linguistics, Louis Hjelmslev (1963: 101). According to him, a human language (his term is dagligsprog) is a language into which all other communication systems (human languages and artificial symbol systems) can be translated. As a consequence of Hjelmslev's theory, an intermediate representation with the expressiveness indispensable for multilingual high-quality machine translation should indeed be itself a human language.</Paragraph>
    <Paragraph position="2"> Now the elements and relations in the semantic system of the intermediate representation can be considered together. The discussion so far has yielded two results: There are no language-independent semantic elements and there are no cross-linguistically valid semantic relations. Moreover, the required expressiveness entails the consequence that the intermediate representation should be a full-fledged language.</Paragraph>
    <Paragraph position="3"> If the pivot of a machine translation system is a language (rather than an artificial symbol system), this removes the problems of spelling out semantic dements and relations. Semantics can then be kept implicit, that is, it can be expressed in tile intermediate language by purely linguistics means, in the way illustrated below.</Paragraph>
    <Paragraph position="4"> If the intermediate language is a full language, the syntactic side of the translation process comes down to performing two direct translations: first from a source language into the intermediate language, and then from the intermediate into a target language. Moreover, if one opts for a human intermediate language, this brings about a substantial change in the design of a pivot-based mnltilingual machine translation system. Artificial intermediate representations are designed to achieve multilingual extensthillty at the level of transfer. The conditions that provide for extensibility are thus directly intertwined with the mechanisms that translate from one particular language into another. But when the intermediate representation is a language, multilingual extensibility shifts to another level: it is now catered for by the combination of language pair modules in which the intermediate language is always one of the two counterparts. This considerably facilitates the design, since mullllingual extensibility with all its needs of cross-linguistically valid grammatical elements and relations no longer interferes with the translation steps proper. For this type of direct translation within a language pair, a translation method that performs the syntactic transfer on the basis of syntactic functions is both suitable and sufficient.</Paragraph>
    <Paragraph position="5"> A possible implementation of this idea is found in the metataxis translation method (Schubert 1987b: 222ff.). It works on the basis of language-specific syntactic functions and contrastive transformation ntles that cater for the transfer step. Metataxis mle,~; can be seen as contrastive lexical redundancy rules ore1' a bilingual dictionary. Teehulcally speaking, they are tree tt~msduction rules which presuppose the dictionary to consist of tree-structured entries. Metataxis is contrastive dependency syntax for translation. Of course it is not the only possible way of performing the syntactic part of a machine translation procedure. A dependency-based approach, however, is esprit\[ally well suited for a multilinguul system, since dependency syntax takes syntactic functions as its primary units, using syntactic form as a secondary means. This is an essential enhancement, since syntactic functions- i.e. dependency retation.s such as subject, object etc. - are translationrelevant, whereas syntactic form characteristics- such as a word's Position vis-~t-vis other words, its endings for case, number, lerson, tense, mood, aspect etc.- are needed for monolingual analysis and synthesis steps in an overall translation proo'.ss, but are not themselves directly translationrelevant). null As for thC/~ semantic side of the translation process, an intermediate representation tempts its designers to make explicit all the semantic distinctionsneeded for specific source and target languages, which ultimately leads astray if mnltilingual extensibility is aimed at. This is the danger of an &amp;quot;exploding&amp;quot; pivot. If the pivot is a language, the degree of semantic detail it provides can be taken as a natural limitation to this explosive tern dency: An implementation is possible in which the entire semantic pn~cessing needed for a machine translation procedure is carried out with linguistic means in the intermediate language only. This means that whatever semantic elements or relations are used, they are always expressed by means of words aria morphemes from the intermediate language. No semantic ll;atures, no selection rules and no meta-linguistic labels or togs are used. This is in good agreement with the metataxis approach to the syntactic side of the process: Metataxis provides all syntactically possible translations of a source sentence (clause, paragraph ._) and the semantic processing performs a choice among these Alternatives. (It normally needs a substanlial pragmatic augmentation witli knowledge of the world etc; ef. Papegaaij/Sehubert forthc.: chapter 3.5.). This semantic process can be carried out entirely in the intermediate language and is titus suitable for metataxis altemative translations generated from whatever source language.</Paragraph>
    <Paragraph position="6"> The second half of the translation, from the intermediate into a target lauguage, could in theory work in the same way, but this would presuppose semantic processing in all the different target lanl,,uages. The requirement of extensibility is much better met, if all the semantic processing for the second half as well is carried out by means of the intermediate language.</Paragraph>
    <Paragraph position="7"> This is indeed possible. The semantic-pragmatic processing in the second half is - to put it in plain words - conceroed with fitting in the alternative translations offered in the bilingual dictionary (intermediate language ---&gt; target language) into the context of the sentence and the entire text. What is needed for assessing the probability of different contexts is information about the typical contexts of the words in question: word expert knowledge. It is possible to describe the typical contexts of target language words by means of words and phrases in the intermediate language. Thus all semantic-pragmatic comparisons and probability computations are carried out exclusively in the intermediate language, and as a consequence only a single semantic system is needed for trattslating between arbitrary languages: a system in the intermediate language, ff rids central system is built up within the limitations of fl~e intermediate language without reference to any peculiarities of p .a.rtieular source and target languages, the requirement of complete extensibility is fulfilled.</Paragraph>
  </Section>
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